1. Field of the Invention
This invention relates to a high frequency signal receiver apparatus of a microwave band, particularly a receiver apparatus using a magnetic oscillator.
2. Description of the Related Art
A high frequency receiver is used for a magnetic recording apparatus to process a signal at several 100 Mb/s to 1 Gb/s or for microwave communication of transmitting and receiving a signal at a transmission rate of several Gb/s. A conventional receiver amplifies a weak digital signal with a low noise preamplifier, subjects the amplified signal to an equalization process such as correction of frequency characteristic, power amplification and out-of-noise cancellation with an equalizer, reproduces an input signal waveform with an identification reproducer, and determines ON/OFF of the signal.
In a conventional high frequency circuit, an equalizer is provided after a preamplifier for the purpose of improving an error rate. However, a noise unable to be removed with the equalizer exists. This adversely affect ON/OFF determination of the input signal. In other words, this reduces the error rate. For this reason, it is necessary to reduce the noise of an amplifier for amplifying an input signal, particularly a preamplifier. For example, it is necessary for receiving a weak signal including only a power corresponding to a heat noise power of about 4 kTΔf to use a high performance heterodyne detection amplifier. However, this amplifier is generally expensive, so that the receiver becomes very expensive.
It is an object of the present invention to provide an inexpensive high frequency receiver apparatus having an excellent error rate.